Engineers at Bucher Hydraulics have developed the UP40 mini power pack with the aim of bringing hydraulic control closer to the drive while providing a more-compact envelope. Compared to other products on the market, the UP40’s dimensions have been reduced to a minimum, said company officials.
The external dimensions of 80 × 80 mm (3.15 × 3.15 in.) are basically defined by the extruded aluminum profiles that are used. The designers made significant efforts to keep within these dimensions while developing various hydraulic circuits. Any components that project outside that profile boundary, for example due to valve contours or accessories, are arranged to extend only on one side.
While the basic size is well defined, the power unit comes in various lengths, as a result of differing lengths of the electric motors and the various capacities of available tanks. The tank consists of a simple, 80 mm diameter extruded aluminum tube which mounts between the front and rear hydraulic control blocks.
The concept is based on a normal mini power pack consisting of an external gear pump driven by a dc electric motor. Oil flow depends on pump displacement, speed of the electric motor, and the respective operating pressure. The gear pump can be a unidirectional or reversible.
The power unit with a unidirectional pump consists of a standard front control block containing an adjustable relief valve and a check valve. These two cartridge valves are types typically required in hydraulic circuits and, exactly for this reason, the engineers decided to integrate them into the front control block. This block is always installed, as it is also the connecting element between the hydraulic pump and electric motor.
From the front hydraulic control block, oil flows through a tube to the rear block, which incorporates the majority of the hydraulic circuit. Various circuit options are included in the company’s catalog.
The single-acting design has a rear control block incorporating a 2/2 seat valve and a pressure compensated 2-way flow control. This arrangement can also be supplemented with an integral emergency hand pump.
This version is often used for laterally mounted under-chassis wheelchair lifts. Thanks to the very compact dimensions of the power unit and its quiet operation, it can also be mounted either inside or outside a vehicle cab (with appropriate safeguards in the case of outside installation).
A version featuring a 4-way spool valve with two or three spool positions for controlling double-acting cylinders is under development. This will also include the ability to fit a double pilot-operated check valve to minimize the effect of leakage that is a characteristic of spool valves.
In contrast, the unit for reversible pumps features a front control block with a double pressure-relief valve and double pressure pipes taking oil to the rear hydraulic control block. The suction-side check valves mount on the rear cover of the gear pump, while the optional double pilot-operated check valve is located on the rear hydraulic control block.
Four standard external gear pumps, for unidirectional or reversible operation, can be used in the UP40. They are part of the Bucher 05 series. They have displacements ranging from 0.25 to 0.9 ccm/rev (0.015 to 0.055 cu.in./rev) and maximum pressure ratings from 200 to 230 bar (2,900 to 3,330 psi). Higher displacements are available, but their power requirements are not matched by the ratings of the electric motors used. Three standard aluminum tanks have nominal capacities from 0.5 to 1.5 l (30.5 to 91.54 cu. in.).
The permanent-magnet electric motors currently available come in 12 or 24 Vdc versions (48 Vdc on demand) with power ratings of 0.5 kW (80 mm dia.) or 0.8 kW (85 mm dia.) and in standard protection class IP54. For specific projects, special configurations with other power ratings and/or protection classes can also be considered.
Thanks to its design, this mini power unit is also ideally suited for direct combination of the power unit and a cylinder into a single unit, according to company officials. As a result, the installation dimensions in machines can be significantly reduced, as there are no extra hydraulic connections. It is also important to note that the UP40 power unit can be installed either horizontally or vertically.
The UP40 mini power unit is particularly suited for areas like hydraulic wheelchair lifts, small tail lifts for trucks, stretchers for special emergency transports, gate openers, capstans, small hand pallet trucks and many other applications where the hydraulic power unit must be extremely compact.